downey



July 16, 1963 w. E. DOWNEY, JR 3,097,404

PROCESS FOR TREATING CARBOLIC OILS Filed July 5, 1960 COKE FURNACE RESIDUE CONC. CARBOLIC OILS NoOH on. 2nd. NoOH lsf. NuOH WASHER DILUTION DILUTION OIL SOLID STRIPPER Na ca CO2 CARBONATOR TAR SETTLING 2 3 SOLUT'ON ACIDS TANK i SOLID M32003 INVENTOR WILLIAM E. DOWNEY, JR.

WM 056w, g5 Cw ATTORNEYS United States Patent 3,tl7,404 PROCESS FOR TREATHJG CARBfiLlC OiLS William E. Downey, in, North Madison, Ohio, assignor to Diamond Alkali Company, Cleveland, Ohio, a corporation of Delaware Filed July 5, 1960, Ser. No. 40,593 Claims. (Cl. 23--63) This invention relates to a method of treating carbolic oil-bearing materials in order to recover the oil and tar acid compounds contained therein and is particularly adapted for the treatment of the tar material recovered as a by-product in the manufacture of coke to recover therefrom phenolic compounds, such as phenols, cresols and xylenols.

Heretofore, it has been the practice to treat carbolic oil-containing materials, and in particular such material recovered as a by-product in the manufacture of coke, with a dilute solution of caustic soda, whereby the sodium salts of the tar acids in the carbolic oil are formed, which sodium salts are soluble in the caustic. Thereafter, the insoluble oils, e.g., benzene, toluene, naphthalene and the like, are separated from the solub-ilized tar acids and the solution of the sodium salts of the tar acids acidified, generally with a carbon dioxide-containing gas, to form the insoluble tar acids. These insoluble tar acids are then separated from the carbonate solution, resulting from the carbonation of the tar lacid salt liquor, leaving a carbonate liquor generally containing 'at least about by weight of alkali metal carbonate and up to about 1% by weight of the tar acids. In that past, the disposition of this alkali metal carbonate solution has been somewhat of a problem, primarily, because of the tar acids contained therein which are considered by public health authorities to be particularly undesirable for discard to public waters.

Heretofore, it has generally been the practice to pass this carbonate solution through a causticizer wherein it is treated With burnt lime to regenerate caustic soda which is then added to the carbolic oil-containing material to solubilize the tar acids contained therein by forming the sodium salts thereof. Although, in such an operation, there is no problem of disposing of tar acid-containing waste material, the equipment and manpower required to operate such a causticizing plant, which is in reality an ammonia-soda plant, are so great as to make thismethod extremely uneconomical to practice. Accordingly, a great deal of time and money has been spent in an attempt to devise some method of utilizing this carbonate liquor which would not involve the necessity of disposing of a waste material containing tar acids.

One method which has been proposed is that of distillation or evaporation of the carbonate liquor so as to recover the tar acids contained therein. However, inasmuch as the tar acids are present generally only to the extent of about 1% by weight of the carbonate liquor and several thousand gallons of carbonate liquor are usually produced each day, such a process is not economically feasible because of the large volume of material which would have to be handled. Another method which has been proposed is the oxidation of the tar acids and the carbonate liquor to innocuous materials, such as CO which would not be objectionable. For this purpose, various oxidizing agents have been proposed, such as, oxygen, permanganates, and chlorine. amount of oxidizing agent which would be necessary to accomplish this oxidation is so large, for example, about 6 tons of chlorine per ton of carbonate liquor, that this process, too, is not economically feasible.

In U.S. Patent 2,686,105, a process is set forth whereby substantially complete precipitation of the tar acids from the carbonate liquor is possible so that the carbonate However, the r 'ice liquor can then be disposed of in any convenient manner with no danger of contaminating natural waterways or public water supply. This method involves a multistep chlorination and oxidation of the solution of tar acid salts and involves first introducing CO and oxygen into the solution until only about -70% of the carbon dioxide necessary to convert the tar acid salts to tar acid have been introduced, at which time any mercaptmis or similar sulphur compounds have been oxidized to insoluble sulphates. The sulphates are then separated and carbonation is continued until substantially complete conversion to the tar acids is obtained. The length of time for this carbonation is set forth as being about 8-10 hours after which time the insoluble tar acids are removed and carbonation may be continued for an additional 2 or 3 hours to effect the formation of solid alkali metal carbonate salt. By this process, it is alleged that the carbonate liquor as well as any solid carbonate removed therefrom is sufficiently free of the undesirable tar acids so that it may be used, if desired, in water treatment. Although, by this process, the problem of disposing of a carbonate liquor containing appreciable quantities of tar acid is eliminated, the carbonation time required to accomplish this is so great that the process cannot be operated continuously.

In view of the above difficulties, none of these processes are deemed to have been completely successful in overcoming the problem of disposing of these tar acid contaminated carbonate liquors and for this reason, in spite of the economic disadvantage in so doing, the causticizing of the liquors to obtain caustic soda is still the most commonly practiced method of treating these materials.

It is, therefore, an object of the present invention to provide an improvement in the method of treating carbolic oil-containing materials wherein the carbonate-containing liquor produced is utilized without the necessity of subjecting it to a causticizing treatment.

A further object of the present invention is to provide an improved method for treating carbonate-containing liquors obtained from the treatment of carbolic oil-containing materials which does not involve the expense of any time-consuming distillation, oxidation, or lengthy calbonation, procedures of the prior art.

These and other objects will become apparent to those skilled in the art from the description of the invention which follows.

The drawing which is attached hereto and forms a part hereof is aschern-atic flow diagram of the method of the present invention.

As used in the description of the invention which follows, the term alkali metal is intended to refer to lithium, potassium, sodium, cesium and rubidium. How ever, because of their low cost and ready availability, the preferred alkali metal compounds are those of sodium. For this reason, hereinafter, specific reference will be made to the compounds of sodium, but this is not intended to be taken as limiting the scope of the present invention.

Additionally, it is to be understood that the term carbolic oils is understood in the art as referring to a mixture of hydrocarbon oils and tar acids. The hydrocarbon oils in this mixture are commonly benzene, toluene, naphthalene and the like, while the tar acids consist mainlyiof phenol and its homologs, such as, cresol and the xylenols. For convenience hereinafter primary reference will be made to the phenolic components of this mixture although such reference is not intended to be taken as excluding the other materials commonly present in such mixture.

In a process for the treatment of a carbolic oil-containing material, wherein a dilute alkali metal hydroxide solution is added to said material to solubilize the tar acids contained therein by forming an alkali metal salt thereof, the insoluble oils being separated from the tar acid salts and the solution of tar acid salts being acidified with carbon dioxide to convert the salts to the insoluble tar acids which are then separated from the alkali metal carbonate solution formed by the carbonation of the tar acid salt solution, the present invention envisions precipitating solid alkali metal carbonate from the thus-separated alkali metal carbonate solution by adding thereto a concentrated alkali metal hydroxide, thus effecting a dilution of the alkali metal hydroxide, separating the thus-precipitated solid alkali metal carbonate and adding the thusdiluted alkali metal hydroxide solution to the carbolic oil-containing material to solubilize the tar acids contained therein, the alkali metal hydroxide being diluted, initially to a point at least suificient so that there is no further precipitation of alkali metal carbonate in the process, prior to the carbonation of the tar acid salt solution, but said alkali metal hydroxide not being diluted, initially, to substantially below by weight.

More specifically, in the operation of the present method, a carbolic oil-containing material, such as, the tar residue from a coke furnace, is treated by admixing therewith a dilute aqueous solution of caustic soda. The caustic soda reacts with the tar acids present in the carbolic oil, forming the sodium salts thereof, such as,

sodium phenolate, sodium cresolate and the like. These sodium salts are soluble in the caustic solution and as much as the oils, such as, benzene, toluene and naphthalene, are not soluble, separation of the oils and acids is thereafter readily effected. After the insoluble oils have been removed from the solution of the tar acid salts, the tar acid salt solution is then acidified by carbonation, preferably with a CO -containing gas. After the carbonation is complete, that is, after substantially all of the tar acid salts have been reconverted to the tar acids, at solution of sodium carbonate is also formed by the carbonation of the sodium hydroxide solution in which the tar acid salts were dissolved. Inasmuch as the tar acids are not soluble in the sodium carbonate solution, separation of the major amount of tar acids therefrom is readily achieved and there is obtained a sodium carbonate solution containing up to about 1% by weight of the tar acid.

This sodium carbonate solution, which generally contains at least about 15% by weight sodium carbonate, and generally about by weight, is then used to dilute a concentrated sodium hydroxide which sodium hydroxide, when diluted, will be added to the coal tar residue to effect springing of the oils and tar acids therefrom. The caustic soda is generally in the form of one of the commercially available concentrated caustic soda solutions which contain 50% by weight or 73% by weight of sodium hydroxide. Upon adding the sodium carbonate solution to the concentrated caustic soda, solid sodium carbonate precipitates from the sodium carbonate solution. Sutficient of the sodium carbonate solution is added to the caustic soda so as to provide a caustic soda solution whose concentration is sufliciently low so that no additional sodium carbonate will be precipitated from the solution when it is used in springing the oils and tar acids from the coke acid residue. However, in order to insure that sufiicient of the sodium carbonate is precipitated from the sodium carbonate solution, it is essential that the caustic soda is not diluted, initially, to a point substantially below about 20% by weight. Generally, Where the causticsoda used is a solution, initially having a concentration of about 50% by weight, it is diluted with the sodium carbonate solution to a concentration within the range of about 2032% by Weight. At this concentration, substantially all, i.e., all but about 6% by weight or less, of the sodium carbonate is precipitated from the solution as solid sodium carbonate. After this initial dilution of the caustic soda, it is generally preferred to further dilute the caustic soda solution to a concentration within the range of about 815% by weight. A1-

4 though this second dilution of the caustic soda solution is not essential, it is found that at the lower concentration of about 815% by weight caustic soda, a more effective springing of the oils and tar acids from the coke furnace residue is obtained.

It will be appreciated by those skilled in the art that the concentration of the caustic soda solution obtained by the first dilution will depend upon several factors. One of the principal factors will, of course, be the amount of sodium carbonate solution which is available. Where the volume of carbonate liquor available is relatively large, the caustic soda solution will be diluted initially to about 20% by weight. Where smaller volumes of carbonate solution are available, the concentration of the caustic solution after initial dilution will generally be higher, e.g., about 32% by weight. It will be appreciated that because of the nature of the process almost invariably, the amount of sodium carbonate liquor available for use in diluting the caustic soda will be less than the amount which is necessary to effect both the first and second dilution of the caustic soda to the preferred 8-15 solution which is used in springing the oils and tar acids. Inasmuch as it is essential that the concentration of caustic soda solution after the initial dilution be sufficiently low that there will be no further precipitation of sodium carbonate in the process prior to the time the tar acid salt solution is carbonated, it may be necessary in operating the process of the present invention to supplement the sodium carbonate dilution solution with water.

Another factor which will aifect the concentration of the casutic soda solution after the initial dilution is, of course, the initial concentration of the caustic soda. Although, for economic reasons, a 50% solution of caustic soda is generally preferred, in some instances, a higher concentration may be used, such as, for example, a 73% solution or even anhydrous caustic soda. Since obviously higher initial caustic soda concentrations will require more diluting liquor, the higher concentration caustic soda may advantageously be used under conditions where a relatively large volume of diluting liquor is available and the need for dilute caustic solutions for springing the oils and tar acids has decreased, as for example, when there is a downward fluctuation in the amount of coke furnace residue to be treated.

It is believed, however, that those skilled in the art can readily ascertain the initial concentration of the caustic soda solution which is to be diluted as well as the concentration thereof after the initial dilution depending upon the conditions which are encountered in each instance. The important factor in the practice of the present invention which must be kept in mind is that the caustic soda is not diluted, initially, to a concentration which is substantially less than about 20% by weight since at concentrations substantially below this amount there will not be a sufiicient precipitation of the sodium carbonate and that, further, the initial dilution of the caustic soda be sufficient that there will be no further precipitation of the sodium carbonate in the process prior to the time the solution of tar acid salts is carbonated. It is to be noted that where this second requirement is not fulfilled and there is an insuflicient initial dilution of the caustic soda, sodium carbonate will be precipitated during the forepart of the springing process and will interfere with the separation of the oils and tar acids.

Referring now to the drawing, which is a schematic flow diagram of the present process, coke furnace residue which nontains carbolic oil is introduced into a washer. Therein it is contacted with a dilute solution of caustic soda, which solution is generally at a concentration of about 8% by weight. In the Washer the caustic soda reacts with the tar acids in the carbolic oil forming the sodium salts thereof, which sodium salts are soluble in the caustic solution. The oil portion of the carbolic oil, which is not soluble in caustic solution, is removed from the washer in any convenient manner. Thereafter, the solution of the tar acid salts is passed into a stripper wherein any of the insoluble oils which were not removed in the Washer are separated from the tar acid salt solution. From the stripper, the solution of tar acid salts is passed into a carbonator wherein it is contacted with a carbon dioxidecontaining gas, generally over a period of about 2 hours. In the carbonator, the solution is acidified and the tar acids are reformed from their salts, which acids are not soluble in the sodium carbonate solution which is also formed in the carbonator. From the carbonator, the mixture of tar acids and sodium carbonate solution is passed to a settling tank from which the insoluble tar acids are removed. It is to be noted, that at this point, as shown by the dotted line, some solid sodium carbonate may be removed from the system, which solid sodium carbonate may be formed in the carbonator depending upon the extent to which the carbonation has been carried out.

After separating the tar acids and any solid sodium carbonate which may have been formed in the settling tank, the sodium carbonate solution is passed to a first dilution tank wherein it is brought into contact with concentrated sodium hydroxide. This concentrated sodium hydroxide is generally in the form of an aqueous solution having a concentration of about 50% by weight sodium hydroxide. In this first dilution tank, the sodium hydroxide is diluted to a concentration preferably within the range of about -32% by weight. At this point, substantially all of the sodium carbonate is precipitated from the solution as solid sodium carbonate and is removed from the dilution tank as shown in the drawing. Thereafter, the caustic soda solution is further diluted, using additional sodium carbonate solution and water, as necessary, to a concentration within the range of about 815% by weight. This dilute caustic soda is then passed into the Washer wherein it is admixed with the coke furnace residue containing the carbolic oil so as to effect a springing of the oils and tar acids from this material.

By the method of the present invention it is possible to use the sodium carbonate solution resulting from the springing of the oils and tar acids from a carbolic oilcontaining material, without the necessity of subjecting the carbonate solution to a causticizing process which is not economical to operate. Additionally, the problems involved in disposing of a carbonate liquor containing small quantities of tar acids, such as, phenols and the like, is overcome without the necessity of subjecting this solution to the expensive step of distillation, oxidation or the like. In order that those skilled in the art may better understand the method of the present invention and the manner in which it may be practiced, the following specific examples are given.

Example 1 A carbolic oil material is passed into a washer at the rate of 33,312 gallons per day. This material contains a total of 34,069 lbs. of tar acids or approximately 1.02 lbs. of tar acid per gallon of carbolic oil material. To this material is added an 8% by weight aqueous solution of sodium hydroxide at the rate of 20,000 gallons per day. From the washer to the stripper is passed an 18% solution of the sodium salt of the tar acids, principally sodium phenolate, at the rate of 30,536 gallons per day. From the stripper, this material is passed to a carbonator wherein it is contacted with a gas containing approximately 20% by weight of carbon dioxide at the rate of 15,646 lbs. of carbon dioxide per day. The tar acid salt solution (sodium phenolate solution) passes through the carbonator in a period of about 2 hours and is collected in the settling tank wherein it remains until a substantially complete separation of the tar acids and sodium carbonate solution is obtained. From the settling tank, the tar acids are recovered at the rate of 34,636 lbs. per day and a sodium carbonate solution, having a concentration of about by weight sodium carbonate, is recovered at the rate of 6 15,142 gallons per day. Thereafter, 1,969.4 gallons of the sodium carbonate liquor are passed through a first diluting tank wherein it is admixed with a 50% aqueous solution of sodium hydroxide which is added to the dilution tank at the rate of 2,288.4 gallons per day. The resulting dilute sodium hydroxide solution in the first dilution tank has a concentration of about 32% by weight sodium hydroxide. From this solution, solid sodium carbonate is precipitated and removed from the first dilution tank at the rate of about 4200 lbs. per day. The 32% sodium hydroxide solution is passed from the first dilution tank into a second dilution tank wherein it. is admixed with the remaining 13,1726 gallons per day of the sodium carbonate solution to which has been added water at the rate of 3,242.8 gallons per day. In the second dilution tank, the 32% sodium hydroxide solution is diluted to a concentration of about 8% by weight sodium hydroxide which 8% solution is passed into the washer for reaction with the carbolic oil, at the rate of 20,000 gallons per day.

Example 2 The process of Example 1 is repeated with. the exception that the sodium carbonate liquor is admixed with the 50% aqueous solution of the sodium hydroxide in the first dilution tank at the rate of 5,251.7 gallons per day. In this manner, the 50% sodium hydroxide solution is diluted to a 20% solution and solid sodium carbonate is recovered from the first dilution tank at the rate of about 8,000 lbs. per day. This 20% caustic solution is then passed into the second dilution tank wherein it is admixed with the remaining 9,890.3 gallons per day of the sodium carbonate solution which has been combined with water at the rate of 3,238.6 gallons per day. The 20% sodium hydroxide solution is thus diluted to a concentration of about 8% by weight, which 8% solution is directed to the washer for reaction with the carbolic oils at the rate of 20,000 gallons per day.

From the above examples, it is seen that by the method of the present invention the sodium carbonate solution resulting from the springing of the oils and tar acids from the carbolic oil-containing material can be utilized to dilute the concentrated sodium hydroxide to the desired concentration for use in-spr-inging the oils and tar acid. Moreover, by using the sodium carbonate solution in this manner, the solid sodium carbonate which is precipitated is found to contain substantially none of the tar acids so that it may be readily disposed of without fear of contaminatingthe disposal area. Additionally, it is found that the amount of sodium carbonate which is present in the sodium hydroxide solution used in springing the oils and tar acid does not adversely affect the reaction of the caustic soda with the tar acids nor is it sufficiently high so as to form a precipitate during the initial stages of the springing processes. It will be appreciated by those skilled in the art that the method of the present invention is readily adaptable to any process which involves the recovering of oils and tar acids from carbolic oil-containing material and although primary reference has been made herein to the treatment of such materials obtained as a residue from coke furnaces, this is intended to be merely illustrative of the manner in which the present process may be utilized. It is further seen that the method of the present invention provides a relatively simple and inexpensive solution to the problem of utilizing the sodium carbonate waste solution obtained in a process for the springing of oils and tar acids and that this process may be readily incorporated into the existing processes for carrying out this operation without the necessity for large capital investments.

While there have been described various embodiments for the invention, the methods described are not intended to be understood as limiting the scope of the invention as it is realized that changes therewithin are possible and it is further intended that each element recited in any of d the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same or equivalent manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. In the process for the treatment of a carbolic oilcontaining material wherein a dilute alkali metal hydroxide solution is added to said material to solubilize the tar acids contained therein by forming the alkali salts thereof, the insoluble oils are separated from the tar acid salts and the solution of tar acid salts is acidified with a carbon dioxide-containing gas to convert the tar acid salts to the insoluble tar acids which are then separated from the alkali metal carbonate solution formed by the carbonation of the tar acid salts, the improvement which comprises precipitating solid alkali metal carbonate from the thus-separated alkali metal carbonate solution by adding thereto a concentrated alkali metal hydroxide of the same alkali metal, thus effecting a dilution of said alkali metal hydroxide solution, separating the thus-precipitated alkali metal carbonate and adding the thus-diluted alkali metal hydroxide solution to the carbolic oil-containing material to solubilize the tar acids contained therein, said alkali metal hydroxide being diluted, initially, to a point at least sufficient that there is no further precipitation of said alkali metal carbonate in the process, prior to the carbonation of tar acid salt solution, but said alkali metal hydroxide not being diluted, initially, to substantially below 20% by weight.

2. The method as claimed in claim 1 wherein the alkali metal hydroxide is sodium hydroxide and the alkali metal carbonate is sodium carbonate.

3. In the method for the treatment of a carbolic oilcontaining material wherein a dilute alkali metal hydroxide solution is added to said material to solubilize the tar acids contained therein by forming the alkali metal salts thereof, the insoluble oils are separated from the tar acid salts and the solution of tar acid salts is acidified with carbon dioxide to convert the salts to the insoluble tar acids which are then separated from the alkali metal carbonate solution formed by the carbonation of the tar acid salt solution, the improvement which comprises forming said dilute alkali metal hydroxide solution which is added to the carbolic oil-containing material by diluting a concentrated alkali metal hydroxide of the same alkali metal, with said alkali metal carbonate solution obtained in the separation of the tar acids, the amount of said alkali metal carbonate solution added being sufficient to dilute said alkali metal hydroxide to a point where no alkali metal carbonates will precipitate after the solution is added to the carbolic oil material but being insufiicient to dilute the alkali metal hydroxide substantially below about 20% by weight, precipitating solid alkali metal carbonate from said alkali metal carbonate solution during said dilution, separating said solid alkali metal carbonate and further diluting the resulting alkali metal hydroxide solution using the remaining portion of said alkali metal carbonate solution, and water as required, so as to obtain an alkali metal hydroxide solution having the desired concentration for adding to the carbolic oil-containing material.

4. The method as claimed in claim 3 wherein the alkali metal hydroxide is sodium hydroxide and the alkali metal carbonate is sodium carbonate.

5. The method as claimed in claim 4 wherein the con centrated sodium hydroxide is first diluted to a concentration within the range of 2032% by weight and is then further diluted to a concentration within the range of about 815% by Weight.

6. The method as claimed in claim 5 wherein the concentrated sodium hydroxide used is an aqueous solution having a concentration of about by weight sodium hydroxide.

7. The method as claimed in claim 5 wherein the concentrated sodium hydroxide is first diluted to a concentration of about 32% by weight and is then further diluted to a concentration of about 8% by weight.

8. The method as claimed in claim 5 wherein the concentrated sodium hydroxide is first diluted to a concentration of about 20% by weight and is then further diluted to a concentration of about 8% by weight.

9. The method as claimed in claim 7 wherein the concentrated sodium hydroxide used is an aqueous solution having a concentration of about 50% by weight sodium hydroxide.

10. The method as claimed in claim 8 wherein the concentrated sodium hydroxide used is an aqueous solution having a concentration of about 50% by Weight sodium hydroxide.

References Cited in the file of this patent UNITED STATES PATENTS 1,971,786 Jones Aug. 28, 1934 2,119,132 Hatman May 31, 1938 2,413,644 Nicholson Dec. 31, 1946 2,597,497 Joris May 20, 1952 

1. IN THE PROCESS FOR THE TREATMENT OF A CARBOLIC OILCONTAINING MATERIAL WHEREIN A DILUTE ALKALI METAL HYDROXIDE SOLUTION IS ADDED TO SAID MATERIAL TO SOLUBILIZE THE TAR ACIDS CONTAINED THEREIN BY FORMING THE ALKALI SALTS THEREOF, THE INSOLUBLE OILS ARE SEPARATED FROM THE TAR ACID SALTS AND THE SOLUTION OF TAR ACID SALTS IS ACIDIFIED WITH A CARBON DIOXIDE-CONTAINING GAS TO CONVERT THE TAR ACID SALTS TO THE INSOLUBLE TAR ACID WHICH ARE THEN SEPARATED FROM THE ALKALI METAL CORBONATE SOLUTION FORMED BY THE CARBONATION OF THE TAR ACID SALTS, THE IMPROVEMENT WHICH COMPRISES PRECIPITATING SOLID ALKALI METAL CARBONATE FROM THE 